Transceivers are sensitive to various signal impairments that affect the quality of the transmitted and received signals. Signal impairments may result from non-idealities in the RF front-ends of the transceivers. For example, mismatched active and passive elements (e.g., quadrature mixers, filters, digital-to-analog converters, and/or analog-to-digital converters) in the I and Q (in-phase and quadrature) signal paths introduce I/Q mismatch impairments in transmitted and received signals. I/Q mismatch, which also may be referred to as I/Q offset, is present in both the transmitter and receiver. In another example, carrier frequency offset in the receiver impairs received signals. Channel effects may also impair signals.
I/Q mismatch introduces an image signal that degrades signal quality. The signal-to-image ratio is typically around 25-30 dB, making I/Q mismatch an issue for systems targeting high spectral efficiency. I/Q mismatch is also frequency dependent, making I/Q mismatch an issue for wideband communication systems.
Accordingly, there is a need for techniques to estimate and compensate for signal impairments.